Semiconductor structure and manufacturing method thereof

ABSTRACT

A semiconductor structure includes a substrate, a first gate structure, a first spacer, a source drain structure, a first dielectric layer, a conductor, and a protection layer. The first gate structure is present on the substrate. The first spacer is present on a sidewall of the first gate structure. The source drain structure is present adjacent to the first spacer. The first dielectric layer is present on the first gate structure and has an opening therein, in which the source drain structure is exposed through the opening. The conductor is electrically connected to the source drain structure, in which the conductor has an upper portion in the opening of the first dielectric layer and a lower portion between the upper portion and the source drain structure. The protection layer is present between the lower portion and the first spacer and between the upper portion and the source drain structure.

PRIORITY CLAIM AND CROSS-REFERENCE

This application is a divisional of U.S. application Ser. No.15/016,144, filed Feb. 4, 2016 and entitled “Semiconductor Structure andManufacturing Method Thereof,” which claims priority of U.S. ProvisionalApplication Ser. No. 62/269,046, filed Dec. 17, 2015 and entitled“Interconnection Structure and Method for Manufacturing the Same,” whichapplications are herein incorporated by reference.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment, as examples. The semiconductor industry continuesto improve the integration density of various electronic components(e.g., transistors, diodes, resistors, capacitors, etc.) by continualreductions in minimum feature size, which allow more components to beintegrated into a given area.

The word “interconnection” in integrated circuits means conductive lineswhich connect the various electronic components. The interconnectingconductive lines are separated from the substrate by insulating layers,except on the contact area. As feature densities increase, the widths ofthe conductive lines and the spacing between the conductive lines ofinterconnect structures also scale smaller.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1-8 are cross-sectional views of a method for manufacturing asemiconductor structure at various stages in accordance with someembodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

The singular forms “a”, “an” and “the” are intended to include theplural forms as well, unless the context clearly indicates otherwise. Itwill be further understood that the terms “comprises” and/or“comprising”, or “includes” and/or “including” or “has” and/or “having”when used in this specification, specify the presence of statedfeatures, regions, integers, steps, operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, regions, integers, steps, operations, elements,components, and/or groups thereof.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed items.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by theperson having ordinary skill in the art. It will be further understoodthat terms, such as those defined in commonly used dictionaries, shouldbe interpreted as having a meaning that is consistent with their meaningin the context of the relevant art and the present disclosure, and willnot be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIGS. 1-8 are cross-sectional views of a method for manufacturing asemiconductor structure at various stages in accordance with someembodiments of the present disclosure.

Reference is made to FIG. 1. A semiconductor structure is formed. Thesemiconductor structure includes a substrate 110, gate structures 121and 123, and at least one source drain structure 130. The gatestructures 121 and 123 are respectively present on the substrate 110.The source drain structure 130 is present on the substrate 110 andadjacent to the gate structures 121 and 123. In other words, the sourcedrain structure 130 is present between the gate structures 121 and 123.It is note that the numbers of the gate structures 121 and 123 and thenumber of the source drain structure 130 are illustrative and should notlimit various embodiments of the present disclosure. A person havingordinary skill in the art may select suitable numbers for the gatestructures 121 and 123 and the source drain structure 130 according toactual situations.

In some embodiments, the substrate 110 may be made of a semiconductormaterial and may include, for example, a graded layer or a buried oxidetherein. In some embodiments, the substrate 110 includes bulk siliconthat may be undoped or doped (e.g., p-type, n-type, or combinationsthereof). Other materials that are suitable for semiconductor deviceformation may be used. For example, germanium, quartz, sapphire, andglass could alternatively be used for the substrate 110. Alternatively,the substrate 110 may be an active layer of a semiconductor-on-insulator(SOI) substrate or a multi-layered structure, such as asilicon-germanium layer formed on a bulk silicon layer.

In some embodiments, at least one stack of a gate dielectric layer, adiffusion barrier layer, a metal layer, a block layer, a wetting layer,and filling metal form at least one of the gate structures 121 and 123.In other words, at least one of the gate structures 121 and 123 mayinclude the stack of the gate dielectric layer, the diffusion barrierlayer, the metal layer, the block layer, the wetting layer, and thefilling metal.

In some embodiments, the gate dielectric layer includes an interfaciallayer (IL, the lower part of the gate dielectric layer), which is adielectric layer. In some embodiments, the IL includes an oxide layer,such as a silicon oxide layer, which may be formed through a thermaloxidation of the substrate 110, a chemical oxidation, or a depositionstep. The gate dielectric layer may also include a high-k dielectriclayer (the upper part of the gate dielectric layer) including a high-kdielectric material, such as hafnium oxide, lanthanum oxide, aluminumoxide, or combinations thereof. The dielectric constant (k-value) of thehigh-k dielectric material is higher than about 3.9, and may be higherthan about 7, and sometimes as high as about 21 or higher. The high-kdielectric layer is overlying, and may contact, the IL.

In some embodiments, the diffusion barrier layer includes TiN, TaN, orcombinations thereof. For example, the diffusion barrier layer mayinclude a TiN layer (the lower part of the diffusion barrier layer), anda TaN layer (the upper part of the diffusion barrier layer) over the TiNlayer.

When one of the gate structures 121 and 123 forms an n-typemetal-oxide-semiconductor (MOS) device, the metal layer is in contactwith the diffusion barrier layer. For example, in the embodiments inwhich the diffusion barrier layer includes a TiN layer and a TaN layer,the metal layer may be in physical contact with the TaN layer. Inalternative embodiments in which one of the gate structures 121 and 123forms a p-type MOS device, an additional TiN layer is formed between,and in contact with, the TaN layer (in the diffusion barrier layer) andthe overlaying metal layer. The additional TiN layer provides the workfunction suitable for the pMOS device, which work function is higherthan the mid-gap work function (about 4.5 eV) that is in the middle ofthe valance band and the conduction band of silicon. The work functionhigher than the mid-gap work function is referred to as a p-workfunction, and the respective metal having the p-work function isreferred to as a p-metal.

The metal layer provides the work function suitable for the nMOS device,which work function is lower than the mid-gap work function. The workfunction lower than the mid-gap work function is referred to as ann-work function, and the respective metal having the n-work function maybe referred to as an n-metal. In some embodiments, the metal layer is ann-metal having a work function lower than about 4.3 eV. The workfunction of the metal layer may also be in a range from about 3.8 eV toabout 4.6 eV. The metal layer may include titanium aluminum (TiAl)(which may include, or free from or substantially free from otherelements) in accordance with some embodiments. The formation of themetal layer may be achieved through physical vapor deposition (PVD). Inaccordance with some embodiments of the present disclosure, the metallayer is formed at room temperature (for example, from about 20° C. toabout 25° C.). In alternative embodiments, the metal layer is formed atan elevated temperature higher than the room temperature, for example,higher than about 200° C.

The block layer may include TiN in some embodiments. The block layer maybe formed using atomic layer deposition (ALD).

The wetting layer has an ability to adhere (and wet) the subsequentlyformed filling metal during the reflow of the filling metal. In someembodiments, the wetting layer is a cobalt layer, which may be formedusing atomic layer deposition (ALD) or chemical vapor deposition (CVD).

The filling metal may include aluminum, an aluminum alloy (e.g.,titanium aluminum), tungsten, or copper, which may also be formed usingphysical vapor deposition (PVD), chemical vapor deposition (CVD), or thelike. The filling metal may be reflowed. The formation of the wettinglayer improves the wetting of the filling metal to the underlyinglayers.

The source drain structure 130 may be formed by doping impurities intoat least one active semiconductor fin, which is formed by, for example,patterning and etching the substrate 110 using photolithographytechniques. In some embodiments that the resulting MOS device is an nMOSdevice, n-type impurities such as phosphorous or arsenic may be doped inthe source drain structure 130. In some other embodiments that theresulting MOS device is a pMOS device, p-type impurities such as boronor BF2 may be doped in the source drain structure 130.

Alternatively, the source drain structure 130 may be formed by, forexample, epitaxial growth. In these embodiments, the source drainstructure 130 may function as a source drain stressor to enhance carriermobility of the semiconductor device and the device performance. Thesource drain structure 130 may be formed using a cyclic deposition andetching (CDE) process. The CDE process includes an epitaxialdeposition/partial etch process and repeating the epitaxialdeposition/partial etch process at least once.

In some embodiments that the resulting MOS device is an nMOS device, thesource drain structure 130 may be an n-type epitaxy structure. In someembodiments that the resulting MOS device is a pMOS device, the sourcedrain structure 130 may be a p-type epitaxy structure. The n-typeepitaxy structure may be made of SiP, SiC, SiPC, Si, III-V compoundsemiconductor materials or combinations thereof, and the p-type epitaxystructure may be made of SiGe, SiGeC, Ge, Si, III-V compoundsemiconductor materials, or combinations thereof. During the formationof the n-type epitaxy structure, n-type impurities such as phosphorousor arsenic may be doped with the proceeding of the epitaxy. For example,when the n-type epitaxy structure include SiP or SiC, n-type impuritiesare doped. Moreover, during the formation of the p-type epitaxystructure, p-type impurities such as boron or BF2 may be doped with theproceeding of the epitaxy. For example, when the p-type epitaxystructure includes SiGe, p-type impurities are doped. The epitaxyprocesses include CVD deposition techniques (e.g., vapor-phase epitaxy(VPE) and/or ultra-high vacuum CVD (UHV-CVD)), molecular beam epitaxy,and/or other suitable processes. The source drain structure 130 may bein-situ doped. If the source drain structure 130 is not in-situ doped, asecond implantation process (i.e., a junction implant process) isperformed to dope the source drain structure 130. One or more annealingprocesses may be performed to activate the source drain structure 130.The annealing processes include rapid thermal annealing (RTA) and/orlaser annealing processes.

In addition, spacers 141 are present on sidewalls of the gate structure121, and spacers 143 are present on sidewalls of the gate structure 123.In some embodiments, at least one of the spacers 141 and 143 include oneor more layers, including silicon nitride, silicon oxynitride, siliconoxide, or other dielectric materials. The available formation methodsinclude plasma enhanced chemical vapor deposition (PECVD), low-pressurechemical vapor deposition (LPCVD), sub-atmospheric chemical vapordeposition (SACVD), and other deposition methods.

Moreover, a hard mask layer 145 is present on a top surface of the gatestructure 121, and a hard mask layer 147 is present on a top surface ofthe gate structure 123. The hard mask layers 145 and 147 may include,for example, silicon nitride or the like. The hard mask layers 145 and147 may be formed using chemical vapor deposition (CVD), physical vapordeposition (PVD), atomic layer deposition (ALD), other suitableprocesses, or combinations thereof.

Then, a dielectric layer 150 is formed on the gate structures 121 and123 and the source drain structure 130. The dielectric layer 150 is aninterlayer dielectric (ILD) layer. The dielectric layer 150 is made of adielectric material, such as silicon oxide, silicon nitride, siliconoxynitride, or combinations thereof. In some embodiments, the dielectriclayer 150 is made of a low-κ dielectric material to improveresistive-capacitive (RC) delay. The dielectric constant of the low-κdielectric material is lower than that of silicon dioxide (SiO2). Oneapproach to reduce the dielectric constant of a dielectric material isto introduce carbon (C) or fluorine (F) atoms. For example, in SiO2(κ=3.9), the introduction of C atoms to form hydrogenated carbon-dopedsilicon oxide (SiCOH) (κ is between 2.7 and 3.3) and the introduction ofF atoms to form fluorosilicate glass (FSG) (κ is between 3.5 and 3.9)reduces its dielectric constant. In some embodiments, the low-κdielectric material is, for example, nanopore carbon doped oxide (CDO),black diamond (BD), a benzocyclobutene (BCB) based polymer, an aromatic(hydrocarbon) thermosetting polymer (ATP), hydrogen silsesquioxane(HSQ), methyl silsesquioxane (MSQ), poly-arylene ethers (PAE),diamond-like carbon (DLC) doped with nitrogen, or combinations thereof.The dielectric layer 150 is formed by, for example, chemical vapordeposition (CVD), spin coating, or combinations thereof.

Reference is made to FIG. 2. A recess 151 is formed at least partiallyin the dielectric layer 150 to expose at least a portion of at least oneof the spacers 141 and 143, while a portion of the dielectric layer 150(the dielectric layer 150 d) is left on the source drain structure 130,in which the dielectric layer 150 d on the source drain structure 130 ispresent adjacent to the spacers 141 and 143 and between the spacers 141and 143. The recess 151 is formed by a photolithography and etchingprocess. The photolithography and etching process includes photoresistapplication, exposure, developing, etching, and photoresist removal. Aphotoresist is applied onto the dielectric layer 150 by, for example,spin coating. The photoresist is then prebaked to drive off excessphotoresist solvent. After prebaking, the photoresist is exposed to apattern of intense light.

The intense light is, for example, a G-line with a wavelength of about436 nm, an I-line with a wavelength of about 365 nm, a krypton fluoride(KrF) excimer laser with a wavelength of about 248 nm, an argon fluoride(ArF) excimer laser with a wavelength of about 193 nm, a fluoride (F2)excimer laser with a wavelength of about 157 nm, or combinationsthereof. A space between the final lens of the exposure tool and thephotoresist surface may be filled with a liquid medium that has arefractive index greater than one during the exposure to enhance thephotolithography resolution. The exposure to light causes a chemicalchange that allows some of the photoresist soluble in a photographicdeveloper.

Then, a post-exposure bake (PEB) may be performed before developing tohelp reduce standing wave phenomena caused by the destructive andconstructive interference patterns of the incident light. Thephotographic developer is then applied onto the photoresist to removethe some of the photoresist soluble in the photographic developer. Theremaining photoresist is then hard-baked to solidify the remainingphotoresist.

-   -   At least one portion of the dielectric layer 150 which is not        protected by the remaining photoresist is etched to form the        recess 151. The etching of the dielectric layer 150 may be dry        etching, such as reactive ion etching (RIE), plasma enhanced        (PE) etching, or inductively coupled plasma (ICP) etching. In        some embodiments, when the dielectric layer 150 is made of        silicon oxide, fluorine-based RIE can be used to form the recess        151. The gas etchant used to dry etch the dielectric layer 150        is, for example, CF₄/O₂. In the example of FIG. 3, a corner of a        portion (e.g., an upper portion) of the spacer 141/143 is        removed by the etching process to form the recess ii. After the        recess 151 is formed, a first portion (e.g., an upper portion)        of each of the spacers 141 and 143 has a sloped sidewall, and a        second portion (e.g., a lower portion) of each of the spacers        141 and 143 has a straight sidewall.

After the recess 151 is formed, the photoresist is removed from thedielectric layer 150 by, for example, plasma ashing, stripping, orcombinations thereof. Plasma ashing uses a plasma source to generate amonatomic reactive species, such as oxygen or fluorine. The reactivespecies combines with the photoresist to form ash which is removed witha vacuum pump. Stripping uses a photoresist stripper, such as acetone ora phenol solvent, to remove the photoresist from the dielectric layer150.

Reference is made to FIG. 3. A protection layer 160 is formed on a topsurface of portions of the dielectric layer 150 (the dielectric layer150 u) on or above the gate structures 121 and 123 (or, on or above thehard mask layers 145 and 147), at least one sidewall of the recess 151(i.e., at least one sidewall of the dielectric layer 150 u and at leasta portion of the exposed spacers 141 and 143), and a bottom surface ofthe recess 151 (i.e., a top surface of the dielectric layer 150 d). Theprotection layer 160 may include, for example, silicon nitride, siliconoxynitride, or the like. In some embodiment, the protection layer 160and the dielectric layer 150 are made of different materials. Theprotection layer 160 may be formed using atomic layer deposition (ALD),other suitable processes, or combinations thereof.

As shown in FIG. 3 and FIG. 4, an anisotropic etching is performed toremove at least portions of the protection layer 160 on top surfaces ofthe dielectric layer 150 u and on the bottom surface of the recess 151(i.e., on the top surface of the dielectric layer 150 d) and a portionof the dielectric layer 150 d while the residual protection layer 160and a portion of the residual dielectric layer 150 d still cover thesidewalls of the recess 151 (i.e., the sidewalls of the dielectric layer150 u and the spacers 141 and 143), and the portion of the residualdielectric layer 150 d is present between the protection layer 160 andthe source drain structure 130. Therefore, the recess 151 is deepened,and the source drain structure 130 is exposed by the deepened recess151. In some embodiments, the anisotropic etching may be dry etching,such as reactive ion etching (RIE), plasma enhanced (PE) etching, orinductively coupled plasma (ICP) etching.

Reference is made to FIG. 4 and FIG. 5. A conductive layer 170 overfillsthe recess 151, such that a bottom conductor 171 is formed in the recess151 and the bottom conductor 171 is electrically connected to the sourcedrain structure 130. The conductive layer 170 is made of metal, such ascopper (Cu), aluminum (Al), tungsten (W), nickel (Ni), cobalt (Co),titanium (Ti), platinum (Pt), tantalum (Ta), or combinations thereof.The conductive layer 170 is formed by, for example, electrochemicaldeposition, physical vapor deposition (PVD), chemical vapor deposition(CVD), or combinations thereof.

Then, the dielectric layers 150 u, the upper portion of the protectionlayer 160 (the height of the upper portion of the protection layer 160is greater than the height of the gate structures 121 and 123 and theheight of the hard mask layers 145 and 147), and the upper portion ofthe conductive layer 170 (the height of the upper portion of theconductive layer 170 is greater than the height of the gate structures121 and 123 and the height of the hard mask layers 145 and 147), whichincludes the upper portion of the bottom conductor 171, are removedthrough a removal process. In some embodiments, the dielectric layers150 u, the protection layer 160, and the conductive layer 170 overburden are removed by a chemical mechanical polishing (CMP) process. Insome embodiments, when the conductive layer 170 is made of copper (Cu),the CMP slurry is made of, for example, a mixture of suspended abrasiveparticles, an oxidizer, and a corrosion inhibitor, and the CMP slurry isacidic. A two-step CMP process may be used to remove the excessdielectric layers 150 u, the protection layer 160, and the conductivelayer 170. In the first step, the abrasive will remove the conductivelayer 170 without disturbing the dielectric layers 150 u and theprotection layer 160. In the second step, the residual dielectric layers150 u, the protection layer 160, and the conductive layer 170 will beremoved using silica abrasive. After the CMP process, the protectionlayer 160 is present between the bottom conductor 171 and the spacer 141and between the bottom conductor 171 and the spacer 143.

Reference is made to FIG. 6. A dielectric layer 180 is formed on thegate structures 121 and 123, the protection layer 160, and the bottomconductor 171. The dielectric layer 180 is an interlayer dielectric(ILD) layer. The dielectric layer 180 is made of a dielectric material,such as silicon oxide, silicon nitride, silicon oxynitride, orcombinations thereof. In some embodiments, the dielectric layer 180 ismade of a low-κ dielectric material to improve resistive-capacitive (RC)delay. The dielectric constant of the low-κ dielectric material is lowerthan that of silicon dioxide (SiO2). One approach to reduce thedielectric constant of a dielectric material is to introduce carbon (C)or fluorine (F) atoms. For example, in SiO2 (κ=3.9), the introduction ofC atoms to form hydrogenated carbon-doped silicon oxide (SiCOH) (κ isbetween 2.7 and 3.3) and the introduction of F atoms to formfluorosilicate glass (FSG) (κ is between 3.5 and 3.9) reduces itsdielectric constant. In some embodiments, the low-κ dielectric materialis, for example, nanopore carbon doped oxide (CDO), black diamond (BD),a benzocyclobutene (BCB) based polymer, an aromatic (hydrocarbon)thermosetting polymer (ATP), hydrogen silsesquioxane (HSQ), methylsilsesquioxane (MSQ), poly-arylene ethers (PAE), diamond-like carbon(DLC) doped with nitrogen, or combinations thereof. In some embodiments,the dielectric layer 180 and the dielectric layer 150 d are made ofsubstantially the same material. The dielectric layer 180 is formed by,for example, chemical vapor deposition (CVD), spin coating, orcombinations thereof.

Then, as shown in FIG. 7, an opening 181 is formed in the dielectriclayer 180 to expose at least a portion of the protection layer 160 andat least a portion of the bottom conductor 171. The opening 181 isformed by a photolithography and etching process. In some embodiments, alayer of photoresist material (not shown) is formed over the dielectriclayer 180. The layer of photoresist material is irradiated (or exposed)in accordance with a pattern (the opening 181) and developed to remove aportion of the photoresist material. The remaining photoresist materialprotects the underlying material from subsequent processing steps, suchas etching. Then, an etching process is performed to form the opening181.

In FIG. 8, a conductive layer 190 overfills the opening 181, and thenthe excess conductive layer 190 outside of the opening 181 is removed.The conductive layer 190 is made of metal, such as copper (Cu), aluminum(Al), tungsten (W), nickel (Ni), cobalt (Co), titanium (Ti), platinum(Pt), tantalum (Ta), or combinations thereof. The conductive layer 190is formed by, for example, electrochemical deposition, physical vapordeposition (PVD), chemical vapor deposition (CVD), or combinationsthereof.

The excess conductive layer 190 outside of the opening 181 is removedthrough a removal process. In some embodiments, the conductive layer 190over burden is removed by a chemical mechanical polishing (CMP) process.In some embodiments, when the conductive layer 190 is made of copper(Cu), the CMP slurry is made of, for example, a mixture of suspendedabrasive particles, an oxidizer, and a corrosion inhibitor, and the CMPslurry is acidic. After the CMP process, an upper conductor 191 (theconductive layer 190) is formed in the opening 181. The upper conductor191 is electrically connected to the bottom conductor 171, and the upperconductor 191 is in direct contact with at least one sidewall of theopening 181.

In another aspect of the present disclosure, a semiconductor structure100 is provided. The semiconductor structure 100 includes a substrate110, gate structures 121 and 123, spacers 141 and 143, at least onesource drain structure 130, at least one dielectric layer 180, at leastone conductor 193, and at least one protection layer 160. The gatestructures 121 and 123 are present on the substrate 110. The spacer 141is present on at least one sidewall of the gate structure 121, and thespacer 143 is present on at least one sidewall of the gate structure123. The source drain structure 130 is present on the substrate 110 andadjacent to the spacers 141 and 143, and the source drain structure 130is present between the spacers 141 and 143. The dielectric layer 180 ispresent at least on the gate structures 121 and 123 and has an opening181 therein, and the source drain structure 130 is exposed at leastthrough the opening 181. The conductor 193 is electrically connected tothe source drain structure 130 at least through the opening 181, and theconductor 193 has an upper portion (i.e., the upper conductor 191) inthe opening 181 of the dielectric layer 180 and a lower portion (i.e.,the bottom conductor 171) between the upper portion of the conductor 193and the source drain structure 130. The lower portion of the conductor193 is at least partially exposed through the opening 181. Theprotection layer 160 is at least present between the lower portion ofthe conductor 193 and the spacer 141 and between the lower portion andthe spacer 143, and the protection layer 160 is at least present betweenthe upper portion of the conductor 193 and the source drain structure130.

Specifically, the upper portion of the conductor 193 is electricallyconnected to the bottom portion of the conductor 193 through the opening181 and at least covers the protection layer 160.

Additionally, the protection layer 160 is present between the lowerportion of the conductor 193 and the gate structure 121 and between thelower portion of the conductor 193 and gate structure 123. Theprotection layer 160 is absent between the upper portion of theconductor 193 and the dielectric layer 180, and the protection layer 160is absent in the opening 181. In other words, the upper portion of theconductor 193 is in direct contact with at least one sidewall of theopening 181 (i.e., at least one sidewall of the dielectric layer 180).

Specifically, a portion of the spacer 141 is present between the gatestructure 121 and the lower portion of the conductor 193, and a portionof the spacer 143 is present between the gate structure 123 and thelower portion of the conductor 193.

The protection layer 160 may be made of a dielectric material, such assilicon nitride, silicon oxynitride, or combinations thereof.Embodiments of this disclosure are not limited thereto. The personhaving ordinary skill in the art can make proper modifications to theprotection layer 160 depending on the actual application.

The height of the protection layer 160 may be in a range from about 5 nmto 2000 nm (i.e., the distance between the top surface and the bottomsurface of the protection 160), and the width of the protection layer160 may be in a range from about 5 Å to about 200 Å (i.e., the distancebetween the two surfaces of the protection 160). Embodiments of thisdisclosure are not limited thereto. The person having ordinary skill inthe art can make proper modifications to the protection layer 160depending on the actual application.

The semiconductor structure 100 further includes a dielectric layer 150d. The dielectric layer 150 d is at least present between the lowerportion of the conductor 193 and the spacer 141 and between the lowerportion of the conductor 193 and the spacer 143. The protection layer160 is present above the dielectric layer 150 d. That is, the dielectriclayer 150 d is present between the protection layer 160 and the sourcedrain structure 130.

The height of the dielectric layer 150 d may be in a range from about 5nm to 1000 nm (i.e., the distance between the top surface and the bottomsurface of the dielectric layer 150 d), and the width of the dielectriclayer 150 d may be in a range from about 5 Å to about 100 Å (i.e., thedistance between the two side surfaces of dielectric layer 150 d).Embodiments of this disclosure are not limited thereto. The personhaving ordinary skill in the art can make proper modifications to thedielectric layer 150 d depending on the actual application.

The semiconductor structure 100 further includes a hard mask layer 145present on a top surface of the gate structure 121 and a hard mask layer147 present on a top surface of the gate structure 123. In other words,the hard mask layer 145 is present between the gate structure 121 andthe dielectric layer 180, and the hard mask layer 147 is present betweenthe gate structure 123 and the dielectric layer 180.

The source drain structure 130 may include at least one source drainstressor. Embodiments of this disclosure are not limited thereto. Theperson having ordinary skill in the art can make proper modifications tothe source drain structure 130 depending on the actual application.

The protection layer 160 can protect the spacers 141 and 143 from beingover-etched during the deepening the recess 151. Therefore, afterformation of the conductor 193, the lower portion of the conductor 193(i.e., the bottom conductor 171) can be electrically isolated from thegate structures 121 and 123 without causing short circuit failuresand/or the leakage problem. With the protection layer 160, the devicesize can be further reduced without putting a heavy load on thephotolithography and etching process, and thus the device performancecan be improved. Furthermore, the overlay and pattern loadingrequirements can be loosened. In addition, the protection layer 160 canenlarge the process window for contact hole formation and improvein-line control in the semiconductor device fabrication process.Therefore, the reliability and/or the yield in fabricating thesemiconductor devices can be improved.

Further, since the upper portion (i.e., the upper conductor 191) and thelower portion of the conductor 193 are formed in different operations,the upper portion of the conductor 193 can be in direct contact with atleast one sidewall of the opening 181. In other words, the upper portionof the conductor 193 is in direct contact with the dielectric layer 180.Therefore, there is no other component present between the upper portionof the conductor 193 and the dielectric layer 180, so the width of theconductor 193 can be greater.

According to some embodiments of the present disclosure, a semiconductorstructure includes a substrate, at least one first gate structure, atleast one first spacer, at least one source drain structure, at leastone first dielectric layer, at least one conductor, and at least oneprotection layer. The first gate structure is present on the substrate.The first spacer is present on at least one sidewall of the first gatestructure. The source drain structure is present adjacent to the firstspacer. The first dielectric layer is present at least on the first gatestructure and has an opening therein, in which the source drainstructure is exposed at least through the opening. The conductor iselectrically connected to the source drain structure, in which theconductor has an upper portion in the opening of the first dielectriclayer and a lower portion between the upper portion and the source drainstructure. The protection layer is at least present between the lowerportion of the conductor and the first spacer and between the upperportion of the conductor and the source drain structure.

According to some embodiments of the present disclosure, a semiconductorstructure includes a substrate, at least one gate structure, at leastone spacer, at least one source, at least one bottom conductor, at leastone protection layer, at least one first dielectric layer, and at leastone upper conductor. The gate structure is present on the substrate. Thespacer is present on at least one sidewall of the gate structure. Thesource drain structure is present adjacent to the spacer. The bottomconductor is electrically connected to the source drain structure. Theprotection layer is present between the bottom conductor and the spacer.The first dielectric layer is present at least on the gate structure andhas an opening therein, in which the bottom conductor is at leastpartially exposed through the opening. The upper conductor iselectrically connected to the bottom conductor through the opening ofthe first dielectric layer and at least covers the protection layer.

According to some embodiments of the present disclosure, a method formanufacturing a semiconductor structure includes the followingoperations. A first dielectric layer is formed on at least one gatestructure and at least one source drain structure. At least one recessis formed at least partially in the first dielectric layer. At least oneprotection layer is formed at least on at least one sidewall of therecess. The recess is deepened to expose the source drain structure. Abottom conductor is formed in the recess, in which the bottom conductoris electrically connected to the source drain structure. The firstdielectric layer, an upper portion of the protection layer, and an upperportion of the bottom conductor above the gate structure are removed. Asecond dielectric layer on the gate structure and the bottom conductoris formed. At least one opening in the second dielectric layer is formedto expose the bottom conductor. An upper conductor is formed in theopening, in which the upper conductor is electrically connected to thebottom conductor.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for manufacturing a semiconductorstructure, the method comprising: forming a first dielectric layer overa gate structure and over a source drain structure adjacent to the gatestructure, wherein a gate spacer extends along a sidewall of the gatestructure, wherein a first portion of the gate spacer is disposedbetween the gate structure and the first dielectric layer, and a secondportion of the gate spacer is disposed between the gate structure andthe source drain structure; forming a recess in the first dielectriclayer over the source drain structure, wherein forming the recessremoves a corner of the first portion of the gate spacer, wherein afterforming the recess, the first portion of the gate spacer has a firstsloped sidewall and a first straight sidewall; forming a protectionlayer over the first dielectric layer and along the gate spacer, theprotection layer lining sidewalls and a bottom of the recess; deepeningthe recess to expose the source drain structure; forming a bottomconductor in the recess and connected to the source drain structure;forming a second dielectric layer over the gate structure and over thebottom conductor; forming an opening in the second dielectric layer toexpose the bottom conductor; and forming an upper conductor in theopening and connected to the bottom conductor.
 2. The method of claim 1,wherein forming the recess comprises removing a first portion of thefirst dielectric layer disposed directly over the source drainstructure, wherein after removing the first portion of the firstdielectric layer, a second portion of the first dielectric layer remainsunder the recess.
 3. The method of claim 2, wherein deepening the recesscomprises performing an anisotropic etch process.
 4. The method of claim2, wherein deepening the recess removes portions of the protection layerover the first dielectric layer, portions of the protection layer liningthe bottom of the recess, and portions of the second portion of thefirst dielectric layer, wherein after deepening the recess, a remainingportion of the protection layer lines upper sidewalls of the recess, anda remaining portion of the second portion of the first dielectric layerlines lower sidewalls of the recess.
 5. The method of claim 4, whereinforming the bottom conductor comprises: filling an electricallyconductive material in the recess after deepening the recess; and afterthe filling, removing a portion of the first dielectric layer disposedover the gate structure, an upper portion of the remaining portion ofthe protection layer, and an upper portion of the electricallyconductive material, wherein a remaining portion of the electricallyconductive material forms the bottom conductor.
 6. The method of claim5, wherein after the bottom conductor is formed, the remaining portionof the second portion of the first dielectric layer extends along asidewall of the gate structure.
 7. The method of claim 1, wherein theprotection layer is formed of silicon nitride, silicon oxynitride, orcombinations thereof.
 8. The method of claim 1, wherein the protectionlayer and the first dielectric layer are formed of different materials.9. The method of claim 8, wherein the first dielectric layer and thesecond dielectric layer are formed of a same material.
 10. The method ofclaim 1, wherein forming the recess comprises performing aphotolithography and etching process.
 11. The method of claim 1, whereinthe recess is formed to have a sloped upper sidewall and a straightlower sidewall.
 12. The method of claim 11, wherein forming theprotection layer comprises forming the protection layer along the slopedupper sidewall of the recess and along the straight lower sidewall ofthe recess, wherein the protection layer has a sloped upper portion withslopped upper sidewall, and has a straight lower portion with a straightlower sidewall, wherein an upper surface of the sloped upper portion ofthe protection layer is level with an upper surface of a mask layerdisposed on the gate structure.
 13. A method for manufacturing asemiconductor structure, the method comprising: depositing a firstdielectric material over a semiconductor device, the semiconductordevice comprising: a gate structure; a mask layer over the gatestructure; a spacer along a sidewall of the gate structure and along asidewall of the mask layer; and a source drain structure adjacent to thegate structure, wherein the spacer is between the gate structure and thesource drain structure, wherein the first dielectric material isdeposited over the mask layer and the source drain structure; forming arecess in the first dielectric material directly over the source drainstructure, wherein after the recess is formed, a first portion of thefirst dielectric material underlies the recess and covers the sourcedrain structure, an upper portion of the spacer has a sloped sidewall,and a lower portion of the spacer has a straight sidewall; forming aprotection layer lining sidewalls and a bottom of the recess; performingan anisotropic etch process to deepen the recess, wherein the sourcedrain structure is exposed after the anisotropic etch process; andfilling the recess with a first conductive material to form a bottomconductor.
 14. The method of claim 13, wherein the anisotropic etchprocess removes portions of the first portion of the first dielectricmaterial, wherein the anisotropic etch process leaves a remainingportion of the first portion of the first dielectric material along asidewall of the spacer.
 15. The method of claim 13, further comprising:after forming the bottom conductor, forming a second dielectric materialover the mask layer and the bottom conductor; forming an opening in thesecond dielectric material to expose the bottom conductor; and fillingthe opening with a second conductive material to form an upperconductor.
 16. The method of claim 13, wherein the recess has a slopedupper sidewall and a straight lower sidewall, wherein the protectionlayer has a sloped upper portion along the sloped upper sidewall of therecess, and has a straight lower portion along the straight lowersidewall of the recess, wherein after the bottom conductor is formed, anupper surface of the sloped upper portion of the protection layer islevel with an upper surface of the mask layer.
 17. A method formanufacturing a semiconductor structure, the method comprising: forminga first dielectric layer over a gate structure and over a source drainstructure adjacent to the gate structure, wherein a gate spacer extendsalong a sidewall of the gate structure and is between the gate structureand the source drain structure, wherein the first dielectric layer isformed along a portion of a sidewall of the gate spacer; forming arecess in the first dielectric layer over the source drain structure, abottom of the recess being between the source drain structure and anupper surface of the first dielectric layer, wherein forming the recessremoves a portion of the gate spacer such that an upper portion of thegate spacer has a sloped sidewall and a lower portion of the gate spacerhas a straight sidewall; forming a protection layer along sidewalls anda bottom of the recess; deepening the recess by an anisotropic etchprocess to expose the source drain structure, wherein the anisotropicetch process removes the protection layer from the bottom of the recess,wherein after the anisotropic etch process, a remaining portion of thefirst dielectric layer extends along the sidewall of the gate structure;filling a first metal in the recess to form a bottom conductor that iselectrically coupled to the source drain structure; forming a seconddielectric layer over the gate structure and over the bottom conductor;forming an opening in the second dielectric layer to expose the bottomconductor; and filling a second metal in the opening to form an upperconductor that is electrically coupled to the bottom conductor.
 18. Themethod of claim 17, wherein forming the recess comprises performing anetching process.
 19. The method of claim 17, wherein after theanisotropic etch process, the protection layer has an upper portion inphysical contact with the upper portion of the gate spacer, and has anlower portion in physical contact with the lower portion of the gatespacer, wherein the upper portion of the protection layer has a slopedsidewall, and the lower portion of the protection layer has a straightsidewall.
 20. The method of claim 17, wherein the first dielectric layerand the second dielectric layer are formed of a same material, whereinthe first dielectric layer and the protection layer are formed ofdifferent materials.